Though more than 1.7 million people living along the Vu Gia River in central Vietnam are suffering from a severe water shortage, an upstream hydropower dam refuses to discharge water, claiming it has no legal obligation to do so.

The Da Nang city administration has complained to the agriculture and industry ministries about Dak Mi 4 hydropower plant's continuing refusal for many years to discharge water during the dry season.

The situation is particularly dire this year because of the entry of seawater and increased salinization in recent months.

The authorities said the salinity only used to be high for a few days between March and August, but last year this stretched to 87 days, and this year the water has been constantly contaminated.

It is affecting nearly one million people in Da Nang and thousands of others in neighboring Quang Nam Province, they said.

Nguyen Minh Chinh, director of the Da Nang Water Company, said the water supply to his plants has dwindled and the salinity levels are excessive.

"We have never experienced the problem for this long."

Since work began on the Dak Mi 4 -- which went on stream last May -- was launched on the Dak Mi River in April 2007, the water flow has been diverted to the Thu Bon River and Vu Gia lost half of its water flow.

Da Nang made numerous requests to the Ministry of Industry and Trade to postpone construction of the dam, and the government in April 2010 ordered the power-plant builders to adjust the design so that it can discharge up to 25 cubic meters a second in case of a water shortage downstream.

Vo Tan Dung, deputy chief manager of the power plant, said the government order pertained to just the design: "There is no regulation forcing us to discharge water in the dry season or how much."

Huynh Van Thang, a Da Nang agriculture official, said since the water level in the dam is 10.7 meters above the dead storage level, it is capable of discharging water.

Dr Nguyen Dinh Hoe of the Vietnam Association for Conservation of Nature and Environment said the investor is putting its interest first and depriving people of water.